Henning,
batsize and batdsksize give you the actual amount of memory allocated by a
BAT which (e.g. due to alignemnent) might be more than the space require to
store all the BUNs that the BAT actually/currently holds:
MonetDB>var b := bat(void,int,1000);
MonetDB>b.info().reverse().like("batBuns").like("size").print();
#---------------------------------#
# h t # name
# str str # type
#---------------------------------#
[ "4000", "batBuns.size" ]
[ "4000", "batBuns.maxsize" ]
MonetDB>b.count().print();
[ 0 ]
MonetDB>b.batsize().print();
[ 8192 ]
MonetDB>b.batdsksize().print();
[ 512 ]
MonetDB>b.append(1).append(2).append(3);
MonetDB>b.info().reverse().like("size").print();
#---------------------------------#
# h t # name
# str str # type
#---------------------------------#
[ "1", "hvarsized" ]
[ "0", "tvarsized" ]
[ "4000", "batBuns.size" ]
[ "4000", "batBuns.maxsize" ]
MonetDB>b.info().reverse().like("batBuns").like("size").print();
#---------------------------------#
# h t # name
# str str # type
#---------------------------------#
[ "4000", "batBuns.size" ]
[ "4000", "batBuns.maxsize" ]
MonetDB>b.count().print();
[ 3 ]
MonetDB>b.batsize().print();
[ 8192 ]
MonetDB>b.batdsksize().print();
[ 1024 ]
Hope this helps you further.
Stefan
On Fri, Oct 05, 2007 at 11:14:31AM +0200, Henning Rode wrote:
> hej monet-people,
>
> i was a bit puzzled when using the batsize/batdsksize mil-commands on
> our pf/tijah index BATs:
>
> our pre_size table is also (void|int). however:
>
> (dbl(batsize("tj_DFLT_FT_INDEX_size1")) /
> count(bat("tj_DFLT_FT_INDEX_size1"))).print();
> [ 5.1875055810700283 ]
>
> since this seemed a rather strange size for an entry, i also tried:
>
> (dbl(batdsksize(bat("tj_DFLT_FT_INDEX_size1"))) /
> count(bat("tj_DFLT_FT_INDEX_size1"))).print();
> [ 4.0000030960842796 ]
>
> which looks much more as i expected. but where does the difference come
> from? even if i copy the bat:
>
> var t := bat("tj_DFLT_FT_INDEX_size1").copy();
> (dbl(batsize(t)) / count(t)).print();
> [ 5.1875055810700283 ]
>
> the result remains the same. can anyone explain this? the pre_size BAT
> is usually so large that 25% more space requirement would probably matter.
>
> best -henning
--
| Dr. Stefan Manegold | mailto:[EMAIL PROTECTED] |
| CWI, P.O.Box 94079 | http://www.cwi.nl/~manegold/ |
| 1090 GB Amsterdam | Tel.: +31 (20) 592-4212 |
| The Netherlands | Fax : +31 (20) 592-4312 |
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